Wireless local area network (WLAN) stations, such as radio network cards and access points, include a medium access control (MAC) layer responsible for a variety of functions that support WLAN operation. In general, the MAC layer manages and maintains communication between WLAN stations. For example, the MAC layer coordinates access to a shared radio channel, and utilizes protocols to enhance communication over a wireless medium. The MAC layer and physical layer (PHY) handle transmission and reception of WLAN packets, and adheres to protocols designed to minimize collision between different stations.
Some wireless networking standards, such as the IEEE 802.11 standards, place many of the functions that are traditionally performed at higher layers of communication stacks in the MAC layer. For example, the IEEE 802.11 standards require that the MAC layer be responsible for scanning, authentication, association, encryption, fragmentation, and power management. Hence, a MAC layer designed for wireless networking may require delivery of high-level functionality in combination with low-level responsiveness. Such divergent requirements can make the design of the MAC layer a balancing act between functionality and performance.